Congenital CMV and Birth Defects

Cytomegalovirus, or CMV, is a very common member of the herpes family of viruses. By age 40, half of the adult population has been infected with CMV. Usually, a CMV infection is short-lived, does not produce noticeable symptoms, and afterward lies dormant in the body for life. But what happens if a pregnant woman picks up CMV for the first time during pregnancy, or has a recurrent infection from a previous exposure? Are there risks to the fetus? And if so, how can your healthcare provider help to minimize these risks?
In this article, we will address the birth defects associated with congenital CMV and ways to protect yourself and your growing baby. If you’d like to know more about CMV during pregnancy in general, check out our article Cytomegalovirus (CMV) Infection.

Congenital CMV Birth Defects:  In The Womb

Not all babies born to CMV-infected mothers develop congenital CMV, and not all that do pick up CMV will experience long-term effects. However, it is important to be aware of the risks because some of them can affect how your child will live his or her life.

What is the risk of passing CMV to my baby during pregnancy?

In general, 1 of every 150 to 200 babies in the USA is born with congenital CMV. This makes CMV the most frequent congenital viral infection. Though this seems like a large percentage of births, only 1 in 5 of these infants born with congenital CMV will experience any adverse symptoms or long-term issues.
The virus has the potential to travel through the mother’s blood and pass through the placenta, infecting the developing baby.

If you have the virus before you become pregnant:  There is a very low chance of passing it to your baby. The chance heightens if you are reinfected with a different strain of the virus (see statistic below), or if you have a reactivation of the virus during your pregnancy.

If you contract the virus (primary infection) during your pregnancy:  It is more likely to pass on CMV to your baby if you get a primary infection during the pregnancy than it is to pass it if you were previously infected. If you have a primary CMV infection during pregnancy, there is approximately a 40% chance of passing the virus to your baby.
The risk of transmission from mother to baby is highest if she gets a primary CMV infection in the third trimester (40-70%) and is lowest if the primary infection begins in the first or second trimesters (30-40%).

Can congenital CMV harm my developing baby?

CMV can pass to your baby at any time during your pregnancy, and any congenital CMV symptoms that are present after birth develop in the womb. So in a sense, yes, CMV can harm your developing baby.
However, the risk of death to a fetus from contracting CMV is extremely small. Doctors have witness seizures in a fetus after contracting congenital CMV, but most of these babies are able to survive and thrive well past birth.
There are quite a few abnormal ultrasound readings that may indicate a congenital CMV infection, including but not limited to:

  • Organomegaly (abnormal organ enlargement) – spleen, liver, and others
  • Abnormal dilation of lateral brain ventricles, the ureter, and/or the renal pelvis
  • Intracranial calcifications
  • Microcephaly
  • Placental thickening
  • Fetal hydrops
  • Ascites
  • Hepatic, intestinal, or periventricular echodensities

One or more of these may indicate congenital CMV; however, many of these abnormalities are linked to a plethora of other diseases or syndromes.

If there are concerns, are there tests to check my baby’s CMV status in utero?

Yes, there is one test that can test your growing baby’s congenital CMV status while still in the womb. This procedure is called amniocentesis, which involves the ultrasound-guided insertion of a needle into the amniotic sac to collect a sample of amniotic fluid for testing. Amniocentesis serves to diagnose a list of genetic abnormalities or diseases.
This testing is usually performed near delivery (end of 3rd trimester) or in the 14-20 week range. Though amniocentesis can give parents and doctors a better idea of any issues or defects the baby may face, there are some risks to the procedure:

  • Miscarriage (1/200 – 1/400 pregnancies using amniocentesis)
  • Infection
  • Amniotic fluid leakage or full break of the sac
  • Accidental poke of the fetus with needle
  • Potential to mix the mother’s blood with fetus’s

If there were any abnormalities on an ultrasound, have a talk with your doctor about your options and the risk to you and your baby with amniocentesis. Many times, the benefits of knowing the results outweigh the risks. This is a personal decision, and not one your doctor can make for you, though he/she may suggest a certain route.
Perhaps the greatest benefit of determining the baby’s congenital CMV status is the potential for rapid treatment following birth. If there are any symptoms of congenital CMV present, the baby may be able to receive faster treatment with antivirals than if testing were performed after birth only.

Are there any treatments if my baby is diagnosed with congenital CMV in the womb?

Although not many, there are a couple of routes you and your doctor(s) can explore after finding out that your developing baby has congenital CMV following amniocentesis.
One option is to ask about using CMV-IGIV. This involves an intravenous (IV) influx of anti-CMV immunoglobulins (IG) or antibodies to help the baby and mother fight a primary CMV infection. This treatment has not (of yet) been proven highly effective, and is not available everywhere.
Another option is to explore any current clinical trials. To research what may be available to you, speak with your doctor, contact the National CMV Foundation here, or visit the National Institutes of Health’s (NIH) clinical trial search.
It is important to remember that not all options are available to everyone, and may depend on your doctor or hospital, accessibility of a proposed treatment, your medical background, the stage of a specific clinical trial, and/or your ability to travel.
Sometimes, the best treatment plan will be to wait until after birth to start the infant on antiviral therapies.

Congenital CMV Birth Defects: Types

Which birth defects are associated with congenital CMV?

The main ways that congenital CMV can affect an infant immediately or overt time are:

  1. Hearing loss
  2. Mental disability
  3. Seizures
  4. Vision loss
  5. Decreased muscle strength (including cerebral palsy)
  6. Decreased coordination
  7. Microcephaly

However, it is important to remember that the majority of infants born with CMV do not suffer any long-term effects or ailments.

What should I expect after birth?

If you and your doctors are aware that you’ve had a reactivation of the virus or primary infection of CMV during your pregnancy, they will take either saliva, urine, or blood sample from your baby in the first 2-3 weeks of life to see if your baby has congenital CMV. These tests check for the live virus or viral DNA rather than for antibodies since the former two are more accurate. They will also look for signs of CMV in your newborn.
Of those infants who test positive for congenital CMV, about 10% of them will have symptoms associated with congenital CMV that are apparent at birth:

  • microcephaly
  • pre-term birth
  • low birth-weight
  • seizures
  • problems with or an enlarged liver or spleen
  • hearing loss

Of that 10% who show signs at birth, 40-60% will have long-term difficulties, such as:

  • hearing loss
  • mental disability
  • vision loss
  • seizures
  • coordination loss
  • decreased muscle tone or ability (including cerebral palsy)
  • calcifications in the brain
  • feeding or sleeping issues
  • death (very rare)

Hearing loss appears to be the only difficulty that may develop later on in infants who have congenital CMV but do not present with symptoms at birth. This accounts for approximately 10-20% of infants with CMV who do not present symptoms at birth.
So, in review:

10% of babies with congenital CMV that are symptomatic at birth will have long-term difficulties of some form.
10-20% of babies with congenital CMV that are NOT symptomatic at birth will have some degree of long-term hearing loss.

Congenital CMV treatment

Congenital CMV Birth Defects:  Treatments & Beyond

Are there any treatments for babies born with symptomatic congenital CMV?

Other than treating the symptoms, the only current treatment available is antiviral medication. Ganciclovir and Valganciclovir are the two options for antivirals, but both have potentially severe side effects. However, if your pediatrician approves, it may be a good and necessary step for your family.

These two antivirals may combat initial symptoms from becoming more severe long-term effects. That does not mean that any and all symptoms will cease, but it could mean a decrease in severity, especially in cases with hearing loss and developmental concerns.

What could a diagnosis of congenital CMV mean for my child, even if they don’t have symptoms at birth?

Babies that receive a diagnosis of congenital CMV after birth yet have no symptoms may have no long-term difficulties at all. However, since some are known to develop over time, the CDC suggests that these children have regularly scheduled hearing and vision checks throughout childhood and adolescence.
Since developmental (mental) delays can also occur months or years after an asymptomatic appearance at birth, your child should be monitored for any signs of developmental difficulty as he/she grows up.

Are there resources to help me as a parent of a child/infant living with a permanent disability from CMV?

Yes, there are! There are quite a few organizations that are specific to congenital CMV and helping parents and their affected children through the symptoms and life changes.
First of all, there are organizations specific to some of the common birth defects of CMV that can help support you on your unique journey:

There are also some organizations specific to congenital CMV support as well:

  • The Congenital CMV Disease Research Clinic & Directory at Baylor in Houston, TX (connection to a parent support network)
  • CMV Blog, Educational downloads, and Parent Stories from the National CMV Foundation
  • (UK) Social Media Support Groups, Resources, Become a Member (with a support team) at CMV Action
  • (AU) Family Support Forum & other Resources at CMV Australia
  • Check out Facebook groups and personal blogs for more personal stories of families affected by congenital CMV

Prevention of CMV Before & During Pregnancy

It’s hard to believe that with so many issues with congenital CMV in the world today, that it is actually a preventable disease. Before and during pregnancy, you can take basic hygiene steps to avoid becoming infected. Prior to pregnancy, you can find out your CMV status.

Before You Become Pregnant:

As you and your partner are planning to conceive, it is a good idea to make yourself aware of your own CMV status. To do this, you can request a CMV antibody test for IgG and IgM (two types of antibodies) from your doctor.
If you test positive for a primary infection (IgG & IgM +), it is suggested to wait until your IgM returns to a low enough level to signify a non-primary infection before trying to conceive (TTC).
If you are either not infected (IgG & IgM -) or have indications of a non-primary/past infection (IgG + and IgM -), then there is usually not a reason to wait to TTC. In the case of no previous infection, the largest concern during pregnancy is a new CMV infection (see “After” for tips on prevention).

After You Become Pregnant:

There is no way to guarantee that you will not pick up CMV or experience a reactivation. However, here are some things that you can do or avoid to reduce your chances of a primary CMV infection.

  • Wash your hands with soap and warm water often, especially:
    • After playing with children
    • After coming into contact with anyone’s, especially children’s, saliva or tears
    • Before touching your face (eyes, mouth, nose – where a virus could enter)
    • After using the restroom
    • After changing a diaper, using a tissue, etc.
  • Eat healthily and exercise during your pregnancy (keeps the immune system strong)
  • Use a condom each time you are sexually active to avoid exchanging fluids
  • Clean children’s toys and counters/handles that children often touch


  • Have sexual contact, including kissing and any type of sex (especially unprotected), with new partners
  • Share drinks or utensils with others
  • Kiss children on the mouth (forehead & cheeks are safer to avoid saliva)

Basically, practicing general hygiene, avoiding new sexual partners, and limiting contact with children’s saliva, tears, etc. can help you avoid CMV.
Women who work in daycares or with children tend to have a higher incidence of contracting CMV. If this applies to you, talk to your doctor about your risk, wash your hands often, and don’t touch your face at work.

CMV and Breastfeeding

You’ve probably heard how beneficial breastfeeding is. But, what about when there’s a concern about the mom having some sort of sickness, like CMV? As always, we suggest speaking with your doctor if you know you’ve had a primary CMV infection during your pregnancy and wish to breastfeed.

If your baby is tested and confirmed for congenital CMV, then there should not be any issues with breastfeeding since both you and the baby already have the virus.

If you know you (1) have/had a primary infection during your pregnancy, (2) may have had a reactivation of the virus, or (3) are high-risk for contracting CMV (ex. work in a daycare), then you will want to have your baby’s test results and, if negative, speak with your doctor before breastfeeding. You may also be able to have your breast milk tested for the live virus.

If your baby does have congenital CMV, then it should be safe for you to breastfeed since transmission has already occurred. A conversation with your doctor will help you weigh the benefits and risks if your baby does not have congenital CMV.

What if my baby gets CMV from me in my breast milk?

Typically, if a baby gets CMV from a mother’s breast milk after birth, there are natural anti-CMV antibodies in the baby’s system. These are passed from the mother to the baby in utero (3rd trimester) or in the breast milk itself. Most infants (and humans of any age) who get CMV do not have any symptoms at all and may be minor if there are any.

When CMV is transferred to an infant through breast milk and/or other fluids after birth, it is termed perinatal CMV.
The greatest concern comes when the infant is preterm and is not born with congenital CMV. Pre-term infants are not expected to have received the full dose of maternal antibodies during the 3rd trimester and are thus less protected against CMV in the breastmilk. The infant may develop more serious (but treatable & temporary) symptoms, such as:

  • enlarged or infected spleen or liver
  • sepsis-like syndrome (can lead to apnea, slow heart rate, or distended abdomen)
  • low platelet count
  • low white blood cell count
  • high liver enzyme amount

Though much of this sounds serious, most infants are able to spontaneously recover. Some may be treated with an antiviral, such as ganciclovir or valganciclovir, to help rid the infection. These medications have the potential for serious side effects, but your doctor will help you decide if the benefits outweigh the risks.

Compiled using information from the following sources:

1. National CMV Foundation.

2. Organization of Teratology Information Specialists (OTIS, 2017): Cytomegalovirus (CMV) Fact Sheet. Available through Mother To Baby.

3. Centers for Disease Control & Prevention: Cytomegalovirus (CMV) and Congenital CMV Infection.

4. Medela Breastfeeding USA: Education Research on CMV.

5. CMV Action